<header>
    什么是行列式？
</header>
<p>
    简单的理解就是数域P上的一个排列，只不过这个排列有点特殊，是一个方阵：
    <code>
        ["matrix",[
          [["rightBottom","a","11"],["rightBottom","a","12"],"...",["rightBottom","a","1n"]],
          [["rightBottom","a","21"],["rightBottom","a","22"],"...",["rightBottom","a","2n"]],
          ["⁝","⁝"," ","⁝"],
          [["rightBottom","a","n1"],["rightBottom","a","n2"],"...",["rightBottom","a","nn"]]
        ],true]
    </code>
    ，这个方阵按照一个规则运算得到一个数，这个数就是这个行列式的值，或者说行列式其实是一个数，只是“外表”有点特殊。
</p>
<p>
    <span class="title">
        定义
    </span>
    n级行列式
    <span class="oneline">
        <code>
            ["matrix",[
                [["rightBottom","a","11"],["rightBottom","a","12"],"...",["rightBottom","a","1n"]],
                [["rightBottom","a","21"],["rightBottom","a","22"],"...",["rightBottom","a","2n"]],
                ["⁝","⁝"," ","⁝"],
                [["rightBottom","a","n1"],["rightBottom","a","n2"],"...",["rightBottom","a","nn"]]
            ],true]
        </code>
    </span>
    等于所有取自不同行不同列的n个元素的乘积
    <span class="oneline">
        <code>
        ["join",
            ["rightBottom","a",["rightBottom","1j","1"]],
            ["rightBottom","a",["rightBottom","2j","2"]],
            "...",
            ["rightBottom","a",["rightBottom","nj","n"]]
        ]
       </code>
    </span>
    的代数和，这里
    <code>
        ["join",["rightBottom","j","1"],["rightBottom","j","2"],"...",["rightBottom","j","n"]]
    </code>
    是1,2,...,n的一个排列，上述每一项都按下列规则带有符号：
</p>
<ul>
    <li>
        当
        <code>
            ["join",["rightBottom","j","1"],["rightBottom","j","2"],"...",["rightBottom","j","n"]]
        </code>
        是偶排列时，带正号；
    </li>
    <li>
        当
        <code>
            ["join",["rightBottom","j","1"],["rightBottom","j","2"],"...",["rightBottom","j","n"]]
        </code>
        是奇排列是，带负号。
    </li>
</ul>